Many pumps utilize either lip-type or labyrinth-type seals to sealingly isolate the bearing frames from exterior contamination. For example, it has been common to utilize lip seals coacting between the bearing frame and the rotatable shaft in an attempt to isolate the bearings from exterior contamination. Such lip seals, however, undergo significant wear, and have also been observed to permit undesirable amounts of moisture to pass thereby. Hence, the life of such arrangements is undesirably low. In this regard, it has been observed that the presence of even small quantities of moisture within the oil reservoir of the bearing frame, such as no more than about 0.002% moisture in the oil, is sufficient to reduce bearing fatigue life by as much as 48%.
To avoid use of lip seals, some pumps have adopted the use of labyrinth-type seals involving closely interfitting stator and rotor rings which do not physically contact but define a narrow labyrinth passage therebetween. While labyrinth sealing devices are in many cases effective for keeping out many types of external contaminants, nevertheless they still permit passage of air therethrough. Due to normal hot/cold cycles, or contact of cool air with the hot equipment, condensation occurs within the bearing frame and hence permits moisture to contaminate the oil.
To resolve this problem, attempts have been made to utilize a sealing device which totally seals the bearing frame. Such attempt has related to the development and use of a magnetic-type mechanical end face seal cooperating between the bearing frame and the rotatable shaft. Such arrangement, an example of which is illustrated by FIG. 1, provides a much improved airtight seal. However, known magnetic-type end face seals have nevertheless still possessed structural or operational features which have severely restricted or limited the application of such devices. For example, the known devices have typically required the use of a separate insulator for mounting the magnetic insert into the bearing frame bore, thereby undesirably increasing the structural complexity and cost. The known arrangement has also typically utilized a conventional elastomeric O-ring for sealingly mounting the magnetic insert within the insulator ring, and such has typically caused the insert ring to tilt or assume an "out-of-square" position which interferes with proper operation of the seal assembly. This "out-of-square" is caused by the elastic distortion or roll of the O-ring during insertion. This known arrangement also typically creates an interior annular space between the opposed seal rings which tends to collect oil, which oil can not properly drain back to the bearing sump, and hence ultimately leaks between the seal faces.
Thus, it is an object of this invention to provide an improved magnetic end face seal assembly which substantially overcomes or improves upon many of the aforementioned disadvantages.
More specifically, the present invention relates to an improved magnetic end face seal assembly wherein the stationary seal ring (i.e., stator) functions as an insert for positioning within the bore of the bearing frame, this insert being a magnetically attractable material, and wherein the rotating seal ring (i.e., rotor) as coupled to the shaft is of a magnetic material and mounts thereon a seal face member which is magnetically urged into sealing engagement with an end face of the seal stator.
In the improved magnetic end face seal, the insert preferably has a seating ring of a hard nonmagnetic material mounted thereon so as to permit direct and substantially rigid but sealed mounting of the insert into the bore of the bearing housing, which support ring also prevents the insert from cocking or going out of square seal.
Further, in the improved magnetic end face the opposed seal faces and their respective supporting rings have substantially identical inner diameters so that the clearance between the shaft and the rings does not create grooves or pockets which tend to trap oil, and such oil can readily drain back to the bearing sump.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.